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Well.... To be fair it's been in the govts interest to not challenge the manufacturers claimed MPG figures, many people wouldn't be buying cars and thus feeding into the coffers if they didn't think their potential new car would give them some benefit in fuel consumption.
Why else was it so important that the govt set about creating the scrappage scheme a few years back?

They are of course idiots anyway, if they think buying a new car can save them money at all.... Even if the old one did 35mpg and the new one 50mpg.

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Yeah this really isnt news, manufacturers make claims for figures but they will have done the test under very specific circumstances that are probably impossible to achieve in reality. Hence I always look at the combined figure and deduct 10% for possible real world driving.

Although on my commute I do get the manufacturers claimed figure for the combined cycle which is what i would describe my journey as. It all depends on how people drive it should be treated as a potential figure. In reality if you drive the right way you can exceed these manufacturers figures in some cars.

The only point for these tests is to compare other cars in the way they have performed in the same test. So you can see with your reading eyes on that a Panda is more economical than a Bentley, that's their only value.
My wifes car persistently hovers around 23mpg and if I take it for a week the average for that fill will be 31-32mpg. Same car, same roads, just different driver.
The manufacturers don't fake the figures (albeit the one production car they test will be in finest fettle), as they aren't so daft as to be officially sanctioned, but real life will always be different.

"The vehicles were then driven by two experienced engineers over a variety of roads"

Unfortunately you need a wider range of drivers to get representative figures. Other major influential factors include the amount of start drop driving (sometimes proxied by average speed), and journey length which partly determines the proportion of distance/time the car spends warming up.

The driving cycles used to measure fuel consumption are designed to simulate these to an extent, but there are so many factors.

How is the fuel consumption test conducted?

The test is outlined in Directive 93/116/EC as amended by Regulation (EC) 692/2008, and provides results that are more than representative of actual average on-road fuel consumption than previous tests. There are two parts: an urban and an extra-urban cycle. The cars tested have to be run-in and must have been driven for at least 1,800 miles (3,000 kilometres) before testing.

Urban Cycle
The urban test cycle is carried out in a laboratory at an ambient temperature of 20oC to 30oC on a rolling road from a cold start, i.e. the engine has not run for several hours. The cycle consists of a series of accelerations, steady speeds, decelerating and idling. Maximum speed is 31mph (50km/h), average speed 12mph (19km/h) and the distance covered is 2.5 miles (4km).

Extra-Urban Cycle
This cycle is conducted immediately following the urban cycle and consists of roughly half steady-speed driving and the remainder accelerations, decelerations, and some idling. Maximum speed is 75mph (120km/h), average speed is 39mph (63 km/h) and the distance covered is 4.3miles (7km).

Combined Fuel Consumption Figure
The combined figure presented is for the urban and extra-urban cycle together. It is therefore an average of the two parts of the test, weighted by the distances covered in each part

Seems like this is PR for What car? than anything else. Any test can be disputed, the point is that all cars must go through identical tests, that is the scientific way of doing it. This allows buyers to assertain what cars are more fuel efficient.

I see that What Car? neglect to mention that some people are able to get better economy than the official figures. The world record in economic driving is something like 30-40MPG higher than the official MPG for that car, which I believe is a VW Passaat

Not a comment on the story, but the headline Government miles-per-gallon car figures 'unreliable' is particularly cringe-worthy. Ignoring the unnecessary hyphens, there are such well-known phrases as "fuel economy" and "fuel consumption" which would be much better.

This is a real problem for company car drivers who are refunded mileage by their employers with rates set by HMRC which are based on these inaccurate figures.

This means that many are seriously out of pocket and there is nothing that can be done. (I have contacted HMRC about this as my car costs 25 pence per mile in fuel but can only claim back 19 pence per mile).

MeanParent first thing is that running around in your own car costs you a darn sight more than the petrol costs, don't do it unless you are properly recompensed! Additionally if they only pay you 19ppm, check out Mileage Allowance Relief.

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